U.S. District Judge Brian Morris put the project on hold Thursday, ruling that the potential environmental impact had not been considered as required by federal law.
Although the decision does not permanently halt the pipeline's construction, it nevertheless comes as TransCanada, the Canadian company that owns Keystone, is preparing to start construction in Montana, shipping pipe to various locations throughout the state, the Great Falls Tribune reports.
According to Carmen, Trump's January 2017 executive order to expedite high priority energy and infrastructure projects, such as the Keystone XL pipeline, is in clear violation of the UN Declaration on the Rights of Indigenous Peoples and the American Declaration on the Rights of the Indigenous Peoples.
Trump, a Republican, said the project would lower consumer fuel prices, create jobs and reduce US dependence on foreign oil.
Noting that former US president Barack Obama had appointed Morris to the court, McConaghy said opponents of the pipeline had "shopped (the case) as best they could to find a pliant federal court judge who had some nexus to the project".
The court has asked the government to review its assessment and revise it, taking into account the changes in the oil markets since 2014, the latest in climate change, and the presence of "cultural resources" along the route of the pipeline that was planned to carry heavy oil from Alberta to US refineries.
"An agency can not simply disregard contrary or inconvenient factual determinations that it made in the past", Judge Morris said in his ruling. "The Trump administration tried to force this dirty pipeline project on the American people, but they can't ignore the threats it would pose to our clean water, our climate, and our communities".
Jauss said a lengthy appellate process could delay TransCanada's goal of beginning construction next year.
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A spokesman for Mr Nelson, Dan McLaughlin, said the lawsuits were politically motivated and "borne out of desperation". Murphy, who swapped his party affiliation from Republican to Democrat in 2011, served in the U.S.
Western Canadian Select crude oil is selling at about $18 a barrel as its discount to USA benchmark West Texas Intermediate as a lack of pipeline capacity bottlenecks production in Alberta.
The 1,897-kilometre pipeline would carry as much as 830,000 barrels of crude per day from Hardisty, Alta., to Steel City, Neb., and on through a half dozen states to refineries on the Gulf Coast.
But it has been the subject of protests for more than a decade, both from environmentalists and Native American groups, who say it will cut through their sovereign lands.
Under President Trump, the State Department wrote "there have been numerous developments related to global action to address climate change, including announcements by many countries of their plans to do so" since the Obama administration's decision two years earlier. There's simply no excuse for approving this bad project.
On another pipeline battlefront, the Nebraska Supreme Court heard oral arguments last week from the attorneys from the pipeline's landowners there - the Ponca Tribe of Nebraska, the Yankton Sioux Tribe and the Sierra Club.
It also used "outdated information" about the impact of potential oil spills on endangered species, he said, rather than the best available scientific and commercial data.
"We keep killing it, and it keeps coming back from the dead", Dallas Goldtooth from the Keep It In The Ground campaign for the Indigenous Environmental Network said, as cited by CBC News.